GB1582535A - Gun - Google Patents

Description

PATENT SPECIFICATION ( 11) 1582535

e' ( 21) Application No 32075/77 ( 22) Filed 29 July 1977 os ( 44) Complete Specification published 7 Jan 1981 ( 19) ( ( 51) INT CL F 41 D 7/06 X ( 52) Index at acceptance F 3 C FC FF ( 54) IMPROVEMENTS IN OR RELATING TO A GUN ( 71) We, PULSEPOWER SYSTEMS INC, a Corporation organized and existing under the laws of the State of California, United States of America, of 815 American Street, San Carlos, California 94070, United States of America, do hereby declare the invention for which we pray that a patent may be granted to us and the method by which it is to be performed to be particularly described in and by the 5

following statement: -

This invention relates to a gun and more particularly to a gun of the kind in which liquid propellant is burned in a combustion chamber to fire a projectile from the gun.

The existing weapons utilised by the armed services generally use solid propellant 10 cartridges, that is to say cartridges in which the propellant is a solid or compressed granular material These existing weapons carry the solid propellant in cases, and the cases form a substantial part of the overall weight and overall size of the cartridge.

This in itself imposes serious drawbacks and limitations on the installation and use of such weapons, because the projectile feed mechanism and related storage facilities 15 must be large enough and strong enough to store and transport not only the projectile itself but also the related solid propellant and case.

Solid propellants have a further inherent disadvantage because of the fact that solid propellants characteristically develop a high peak temperature In many gun installations it is necessary to fire long bursts in multiple engagements, for example 20 when a gun installation fires on a large number of enemy ships, or bombards a piece of territory for a long period of time before troops advance into that territory Such projected firing schedules produce severe thermal loads on the gun and often cause barrel erosion or deformation with the existing solid propellant weapons.

Automatic guns used in anti-aircraft roles are a good example of guns subjected 25 to severe firing schedules Long bursts are needed to, achieve high cumulative kill probabilities These gun systems must also engage multiple targets in rapid succession with little or no time between bursts for adequate cooling A severe barrel cooling problem results which is a primary factor in limiting system effectiveness The reduced accuracy associated with premature barrel erosion can effectively destroy gun capability 30 during a single engagement The alternative is to increase the number of available mounts to achieve an acceptable firing schedule This results in additional weight, complexity, cost and maintenance problems, and is therefore an unacceptable solution.

The problem has long been recognised in high performance, gun installations such as the U S Navy 40 mm Bofors automatic gun and Oto Melara 76/62 In both 35 cases a classic approach to barrel cooling has been taken, i e water jacketing of the exterior barrel surface However, even with exterior water jacketing, the heat transfer rate may be too, limited for some applications.

The problems of severe thermal loads and barrel erosion also occur in drilling by cannon excavation In cannon excavation the firing rate is relatively low but the 40 duty cycle is sustained for long periods of time, and this produces severe thermal loads on the barrel.

It is one important object of the present invention to provide a more effective means for cooling.

There are a number of recognized technical objectives for high performance guns 45 In general, these include: ( 1) high velocity and rate of fire; ( 2) low gun and ammunition weight; ( 3) good interior and exterior ballistic performance; ( 4) low erosion, flash and smoke; ( 5) low recoil loads; ( 6) elimination of cases, links and sabots; ( 7) good reliability and safety; and ( 8) versatility-application to a wide range or requirements 50 In addition to these general criteria, the following characteristics are recognized as being factors lacking in the prior art and needed to enhance the applicability of future gun systems as compared to the prior art: ( 1) a gun of minimum cross section to assure maximum versatility of installations on shipboard, vehicle and aircraft mounts; ( 2) an envelope that will assure retrofit capability of single or multibarrel high performance 30 or 35 mm liquid propellant guns in existing 20 mm installations; ( 3) a 5 mechanism design capable of employing high density, low drag projectiles currently in the inventory or in an advanced stage of development; ( 4) at the 30/35 mm scaleutilization of existing projectile designs (with only minor modifications) to eliminate immediate requirements for development of new projectiles, and muzzle velocities in excess of 4000 ft per second employing high sectional density projectiles to provide 10 adequate standoff, short time of flight, and high projectile payload; ( 5) a gun mechanism construction adaptable to operation at higher muzzle velocities when adequate projectiles are available; ( 6) stationary barrel construction with rotating cam feed mechanism to provide significant reduction in gun drive power requirements and quicker acceleration to full firing rate; ( 7) simplified gun harmonization at all 15 firing rates by elimination of tangential projectile velocity components associated with rotating barrel systems.

A further requirement which has been placed on gun development in guns of this size range is that the gun must be applicable across the board to sea, air and ground needs for the three services These include (but are not limited to) small craft point 20 defence, landing craft armament, retrofit of existing fixed wing aircraft and antiaircraft and anti-vehicle ground applications where rate of fire and configuration constraints vary widely Some missions require single barrel guns with relatively low, adjustable rates of fire ( 0 to 1000 rounds per minute) Others involve multibarrel installations at intermediate rates of fire ( 2000 to 3000 rounds per minute), and finally 25 there are those which require very high rates of fire ( 4000 to 6000 rounds per minute).

It can be seen that this range of rate of fire indicates that automatic guns are needed having from one to eight barrels.

Liquid propellant guns have a characteristic low peak temperature Because a liquid propellant will ignite in the bulk mode, it can be ignited, as by an electrical 30 spark device immersed in the liquid propellant, without the need to vaporize the propellant prior to ignition Liquid propellants are high energy density liquids and can be burned in discrete pulses to produce high combustion pressures Pulsed burning of a liquid propellant can produce combustioni pressures in the range of 10,000 to 80,000 psi and even higher The magnitude of the average combustion pressure in 35 such pulsed burning can be controlled by the amount of expansion permitted Higher average combustion pressures can be produced by permitting less expansion.

The liquid propellant gun can produce a flatter combustion chamber pressure-time characteristic than a solid propellant gun Hence, performance equivalent to a solid propellant gun can be obtained at lower pressure High cyclic rates of fire are possible 40 with a liquid propellant gun Because the propellant is a liquid, the propellant can be easily pumped to the firing chamber from a storage area remote from the gun itself.

This permits flexibility of installation Because the cartridge feeding system of the liquid propellant gun carries only the projectile itself, the projectile feed system can be simplified and can be made considerably lighter in weight than for a con 45 ventional gun Or, a considerably larger projectile size and weight can be used for higher performance without having to increase the size of the projectile feed mechanism.

This is especially important in permitting larger bore liquid propellant guns to, be incorporated in retrofit installations as replacements for existing smaller bore solid propellant guns 50 Liquid propellant guns also permit slim profiles which provide desirable configuration versatility Because the liquid propellant gun permits a low profile, clean exterior design, an individual liquid propellant gun module or a modular grouping of liquid propellant gun modules can be installed in locations that would not accommodate a conventional gun 55 It is another important object of the present invention to incorporate the inherent advantages of a liquid propellant gun in a modular gun of the kind incorporating a drive cam and a control cam.

According to one aspect of this invention there is provided a gun of the kind in which liquid propellant is burned in a combustion chamber to fire a projectile from 60 the gun and comprising a gun barrel, a combustion chamber, a bolt mounted for axial movement between a rearward, projectile loading position and a forward, projectile firing position, liquid propellant injection means for injecting a liquid propellant into the combustion chamber, igniter means for igniting the liquid propellant in the combustion chamber, drive cam means for moving the bolt back and forth between the 65 1,582,535 rearward and forward positions, drive means for driving the drive cam means, and control means for controlling the liquid propellant injection means and igniter means in coordination with the drive of the drive cam means.

Preferably the gun is of the kind in which liquid propellant is burned in a combustion chamber to fire a projectile from the gun and wherein said firing chamber 5 comprises a combustion chamber at one end of the gun barrel, there being liquid propellant injection means for injecting a liquid propellant into the combustion chamber, and igniter means for igniting the liquid propellant in the combustion chamber.

Cooling is achieved in this aspect of the present invention by internal water cooling The way in which the internal water cooling is incorporated in a liquid pro 10 pellant gun in, accordance with this aspect of the present invention also permits the mechanism for injecting the water for cooling to be used as a water purge system for purging the combustion chamber of liquid propellant in the event of a misfire.

At this point the applicants would like to point out that, because the water does impinge directly on the heated gun bore surfaces in embodiments of this 15 aspect of the present invention, high heat transfer rates are realized and the effectiveness of the internal water cooling permits significant increase in burst length and frequency in automatic guns It also permits a significant increase in length of the duty cycle in such applications as drilling by cannon excavation.

According to a further aspect of this invention there is provided a method of 20 firing a projectile from a gun of the kind in which a liquid propellant is burned in a combustion chamber, said method comprising the steps of locating a projectile in said gun, moving a bolt axially from a rearward, projectile loading position to, a forward, projectile firing position, by a drive cam means driven by a drive means, injecting liquid propellant into the combustion chamber, igniting the liquid propellant in the 25 combustion chamber, the injection and ignition of the liquid propellant being controlled in coordination with the drive means, and thus in coordination with movement of the bolt.

One embodiment of a liquid propellant gun in accordance with the present invention is a cam operated, externally driven gun constructed in modular form It 30 has a slim profile, and the operational features of the gun are arranged so' that the gun can be readily incorporated in a variety of modular clusters, such as flat pack groupings and circular groupings The guin barrel is stationary and all combustion chamber pressure loads on the bolt are carried through the barrel rather than being carried through the receiver with the result that the receiver can be made quite light 35 The gun incorporates two cams, a drive cam and a control cam The drive cam reciprocates the bolt back and forth between a rearward, projectile loading position and a forward, projectile firing position The drive cam is a hollow cylindrical member having two spiral cam tracks formed on the inside of the drive cam The first spiral cam track engages a cam follower on the bolt to drive the bolt forward, and the other 40 spiral cam track engages the cam follower to drive the bolt rearward as the drive cam is rotated about the axis of reciprocation of the bolt.

The control cam is located at the front end of the drive cam, and the control cam is also an annular member which is rotated about the axis of the bolt The control cam controls the injection of the liquid propellant into the combustion chamber and 45 also controls the igniter for igniting the propellant The drive cam is rotated faster than the control cam and has dwell or rest areas at each end of the drive cam to provide the time intervals for the projectile loading at one end and the propellant injection and firing at the other end of the bolt's reciprocation The drive cam rotates the bolt in one direction at the end of its forward travel to lock the bolt to the barrel, 50 and the control cam rotates the bolt in the opposite direction after firing to unlock the bolt from the barrel The axial sliding movement of the reciprocating bolt is guided by lugs on the bolt which interfit in slots in the barrel extension or receiver of the gun.

The cam follower of the bolt is mounted for a limited amount of radial movement 55 with respect to the bolt to accommodate, by outward movement, the bolt rotation required to lock the bolt and, by inward movement, the required dwell at the forward end of the bolt travel The barrel extension has a cam surface that coacts with the cam follower and a dwell area at the forward end of the drive cam to provide the required dwell in this part of the cycle of operation of the gun, The control cam 60 unlocks the bolt and returns the cam follower to the rearward, spiral drive cam track at the proper time.

The drive cam and the control cam are driven in synchronism by interconnected gearing, and the drive cams of adjacent gun modules are interconnected by idler gears for transferring drive from one module to the next 65 1,582,535 4 1,582,535 4 A preferred embodiment of a gun in accordance with the present invention incorporates a water cooling arrangement in which the control cam causes a small amount of water to be injected into the combustion chamber after the firing of each round.

The injected water is vaporized and converted to steam as it contacts the hot combustion chamber structure, and this produces a highly effective cooling of the combustion 5 chamber structure.

Preferably the water cooling valving is interconnected with the valving for the propellant injection in a manner such that the combustion chamber can be completely filled with water to purge the combustion chamber of propellant in the event of a misfire 10 The preferred gun incorporates misfire detection means which coact with the control cam to completely disengage the control cam from the drive so'that operation of the gun module is stopped in the event of a misfire.

In order that the invention may be more readily understood and so that further features thereof may be appreciated the invention will now be described by way of 15 example with reference to the accompanying drawings in which:

Figure 1 is an isometric view of a liquid propellant gun module constructed in accordance with one embodiment of the present invention; Figure 2 is an isometric view showing three of the gun modules of Figure 1 grouped in a flat pack cluster; 20 Figure 3 is an isometric view showing three of the gun modules of Figure 1 grouped in a circular cluster; Figure 4 is a side elevation view of the gun module shown in Figure 1; Figure 5 and Figure 5 a is an enlarged top plan view of the gun module taken along the line and in the direction indicated by the arrows 5-5 in Figure 4, some 25 parts being partly broken away to show details of construction, Figure 5 a being a continuation of the left hand end of Figure 5; Figure 6 and Figure 6 a is a side elevation view in cross section taken generally along the line and in the direction taken by arrows 6-6 in Figure 5 and Figure 5 a, Figure 6 c being a continuation of the left hand end of Figure 6, and the cam follower 30 64 being shown rotated 300 in Figure 6 for better illustrating its operation; Figures 7-14 are end elevation views in cross section taken along the lines and in the direction indicated by the correspondingly numbered arrows in Figure 6, the true position of cam follower 64 being illustrated in Figure 13; Figure 15 is an end elevation view taken along the line and in the direction 35 indicated by the arrows 15-15 in Figure 4; Figures 16-21 are isometric views showing the disposition of certain parts of the gun in the various phases of operation indicated by the legends in these Figures; Figure 22 is a fragmentary, enlarged view of the part of the structure shown encircled by the arrows 22-22 in Figure 6, the cam follower (as in Figure 6) being 40 shown rotated 300 from its actual position illustrated in Figure 13; Figure 23 is a fragmentary, enlarged end elevation view taken along the line and in the direction indicated by the arrows 23-23 in Figure 22, but with the cam follower at the actual inclination illustrated in Figure 13; Figure 24 is a fragmentary, enlarged end elevation view taken along the line and 45 in the direction indicated by the arrows 24-24 in Figure 22 showing the cam follower 64 in the unlocked position in phantom outline and in a locked position in bold outline; Figure 25 is a fragmentary, enlarged bottom plan view taken along the line and in the direction indicated by the arrows 25-25 in Figure 23; 50 Figure 26 is a fragmentary enlarged side elevation view taken along the line and in the direction indicated by the arrows 26-26 in Figure 5, and showing the positions of the water injection and the propellant injection control valves during firing of the gun; Figure 27 is a fragmentary enlarged side elevation view like Figure 26 but showing 55 the positions of the water injection and propellant injection control valves during propellant loading; Figure 28 is a view like Figures 26 and 27 but showing the positions of the water injection and propellant injection control valves during either the combustion chamber cooling or the emergency purge operations; 60 Figure 29 is a fragmentary, enlarged view of the front face of the control cam and is taken generally along the line and in the direction indicated by the arrows 29-29 in Figure 19, and shows the recess in the control cam for the control of the propellant injection, the projection on the control cam for the water injection and a projection on the control cam for controlling the operation of the igniter; 65 1,582,535 5 Figure 30 is a fragmentary enlarged plan view taken generally along the line and in the direction indicated by the arrows 30-30 in Figure 29; Figure 31 is a top plan view showing five gun modules assembled in a flat pack cluster together with a drive motor for the gun modules and the projectile feed system; 5 Figure 32 is an end elevation view taken generally along the line and in the direction indicated by the arrows 32-32 in Figure 31, and shows the feeding of specific projectiles in the endless conveyor belt to related gun modules; Figure 33 is an end elevation view like Figure 32 but showing, the projectile feed system for three gun modules assembled in a circular cluster; 10 Figures 34-39 illustrate different cluster configurations for the modular gun of the present invention and illustrate how projectile feed systems are associated with these different cluster configurations; Figure 40 is a plan view showing a size comparison for high performance 30 mni liquid and solid propellant rounds of ammunition and also illustrates the relative feed 15 chute sizes required; Figure 41 is a top plan view showing a size comparison of a 30 mm liquid propellant projectile, a conventional solid propellant 20 mm round for an M 61 Vulcan gun and a conventional solid propellant round for a 30 mm Hispan Suiza round type $ 31 L, this Figure illustrating how a 30 mm liquid propellant round is approximately 20 the same overall length as a conventnsolid'piopelant 20 mm round and how it is therefore capable of being substituted in conventional projectile feed systems for smaller 20 mm solid propellant rounds with a minimum of retrofit modifications; Figure 42 is a fragmentary and elevation view showing details of the misfire switch and control cam shifting lug; 25 Figure 43 is a fragmentary side elevation view taken along the line and in the direction indicated by the arrows 43-43 in Figure 42; and Figure 44 is a schematic view of a pressure sensing interlock system for stopping operation of a gun module in the event of a drop in propellant feed pressure.

One embodiment of a liquid propellant gun module constructed in accordance 30 with the present invention is indicated generally by the reference numeral 50 in Figures 1, 4, 5, 6 and 16 to 21.

As shown in Figures 6 and 6 a, the gun module 50 includes a barrel 52, a combustion chamber 54, a bolt 56, a barrel extension or receiver 58, a drive cam 60, a control cam 62, a cam follower 64, a projectile loading mechanism 66 for loading 35 projectiles from a projectile feeding mechanism 68 (Figure 5), a drive mechanism 70, propellant injection means 72, water coolant and purge means 73, a bolt sear 74, an igniter 76, misfire detection means 78 (Figure 5 a) and a misfire switch 80, all as indicated generally by these reference numerals in Figures 5 and 6 and in other Figures of the drawings 40 The gun module 50 illustrated in the drawings uses a liquid monopropellant (i e.

a liquid propellant that contains both a fuel and an oxidizer) in the combustion chamber 54 for firing a projectile 84 It should be noted, however, that many of the features of the present invention are not limited to, a modular gun or to a gun using a monopropellant, as will become more apparent from the description to follow 45

The bolt 56 is reciprocable back and forth between a rearward, projectile loading position (see Figure 16) and a forward, projectile firing position (see Figs 18, 19 and 20).

The bolt is guided in this reciprocating movement by lugs 86 (see Fig 17 and Fig 9) which slide within guide slots 88 (see Figs 19 and 11) in the barrel extension 50 58 and guide slots 90 (see Fig 18 and Fig 10) extending through locking lugs 92 at the rear end of the barrel 52.

The igniter 76 is located in the front face of the bolt 56 and comprises an electrode 91 (see Fig 6 and Fig 11) which is energized when a cam follower (not illustrated) is displaced by a projection 94 on a forward control face 96 of the control cam 62 55 (see Figs 29 and 30) Energization of the electrode 91 produces electrical energy which ignites the liquid propellant in the combustion chamber 54 to' fire the projectile 84 out of the barrel 52 Ignition can also be accomplished by compression ignition or by injecting a chemical into the propellant.

The forward face of the bolt 56 has a seal 96 as best illustrated in Fig 6 60 The rear end of the bolt 56 has a bolt extension 100 which coacts with the projectile loading mechanism 68 to snap a projectile out of a spring clip carrier in the projectile feed mechanism 66 (in a way to be described in more detail below) when the bolt is moved to the rearward, projectile loading position.

The bolt extension 100 also has a detent 102 which is engaged by the pawl of the 65 sear 74 to hold the bolt in the rearward position when the gun trigger is off and a sear solenoid 104 is deenergized.

A sear actuating rod 106 is connected to the rear solenoid 104 and has a slot 108 (see Figure 6) A pin 110 connected to the lower end of the pivot arm 112 of the sear 74, rides in the slot 108 The arm 112 pivots about a sear pivot 114 which 5 straddles the spring cavity As illustrated in Figure 6, a spring 116 normally biases the sear pawl 74 toward a bolt retaining position, but energization of the sear solenoid 104 rotates the pawl 74 downward to the bolt releasing position (best illustrated in Figure 21).

The end face 118 of the bolt extension 100 is engageable with a face 120 of a 10 spring backed part 124 which actuates the projectile loading mechanism 66 The back face of the part 124 provides a spring seat for one end of a bolt return spring 126.

(see Figure 6) The other end of the bolt return spring 126 is seated against an inner face of a rear cover 128.

The part 124 has an upwardly projecting flange 129 which is engageable with is an actuator lever 130 of the projectile loading mechanism 66 The upper end of the actuator lever 130 is connected to a push rod 132 by a pin joint connection 134, and a spring 136 maintains the lower end of the actuator level 130 in engagement with the upwardly extending flange 129.

The front end of the push rod 132 is connected to a bellcrank loading lever 138 20 by a pin joint connection 140 The downwardly extending arm of the bellcrank projectile loading lever 138 is pivotally connected to the barrel extension 58 by a loading lever pivot 141.

The forwardly extending arm of the projectile loading lever 138 has a lower end 142 which is positioned over an upper recess 144 in a spring clip carrier 146 25 for a projectile 84 This projectile is aligned with the upper end of a projectile receiving passageway 148 in the barrel extension 58 (see Figs 10 and 11).

Engagement of the bolt extension 100 with the part 124 moves the lower end of the actuator lever 130 about the pivot provided by the connection to the spring 136 to shift the rod 132 forward This pivots the bellcrank 138 about the pivot 141 30 and snaps a projectile 84 out of the spring clip carrier 146 of the endless conveyor belt 149 (see Fig 32) of the projectile feed mechanism 68.

The projectile drops into the passageway 148 and into the bore in the barrel extension in front of the bolt 56 Forward movement of the bolt 56 then pushes the projectile up into the barrel 54, and the projectile 84 is then pumped forward 35 (to the position illustrated in Fig 6) against the forcing cone 150 by the liquid propellant injected into the combustion chamber This will be described in greater detail below.

The barrel 52 is connected to the barrel extension 58 by cap screws 152 (see Fig 6).

A cam cover 154 is connected to the barrel extension 58 by cap screws 156 as also 40 shown in Fig 6.

The drive cam 60 has two internal, spiral shaped, cam paths 160 and 162 which are engageable with the cam follower 64 for reciprocating the bolt 56 forward and backward during operation of the gun The spiral cam track 160 drives the bolt 56 forward, and the spiral cam track 162 drives the bolt 56 rearward 45 The drive cam 60 is axially elongated so that the cam angles are not too high, and the drive cam is rotated faster than the control cam 62.

As best shown in Figs 1-3 and 31, the drive system 70 includes a drive motor 164 The drive motor 164 rotates an idler gear 166, and the idler gear 166 is engaged with a gear 168 formed on the outer diameter of the drive cam 60 at the 50 rear end of the drive cam 60.

Fig 15 illustrates how this same idler gear 166 is used to transfer the drive from one module to an adjacent module in a cluster arrangement.

The drive to the control cam 62 is provided by a jack shaft take off gear 170 which engages gear 168, a jack shaft 172, a jack shaft pinion gear 174 (see Fig 13), 55 an idler gear 176 and a gear 178 formed on the outer diameter of the control cam 62 (as best illustrated in Figs 6 and 16 to 21) The control cam 62 is therefore rotated in a direction opposite from that of the drive cam 60, as indicated by the arrows in Fig 17.

In a particular embodiment of the present invention the gear ratios are such that 60 the drive cam 60 is rotated four times as fast as the control cam 62. The drive cam 60 is mounted for rotation on the barrel extension 58 by

bearings at the rear end of the drive cam and 181 at the forward end of the drive cam (see Fig 6).

The control cam 62 is mounted for rotation on a surface 182 of the barrel exten 65 1,582,535 7 1,582,535 7 sion 58 and is normally retained in a fixed axial position with respect to the barrel extension 58 by two radially projecting cam lobes 184 on the outer periphery of the control cam 62 (see Fig 12) The lobes 184 travel in an annular groove 186 in the barrel extension 58 In normal operation of the gun the lobes 184 travel in the groove 186 and the control cam 62 is maintained in the fixed axial position illustrated 5 in Fig 6 with the gear 178 engaged with the gear 176 However, the barrel extension 58 has a relieved space 188 in front of the control cam which permits the control cam to be shifted axially forward and disengaged from the drive connection with the idler gear t 76 in the event of a misfire In this condition of operation as illustrated in Fig 43 and as will be described in more detail below, the misfire switch 80 engages 10 one of the cam lobes 184 to move the control cam 62 forward The cam lobe that engages the misfire switch is diverted into a dead end side track 187, and the other lobe 184 enters a relieved area.

As best illustrated in Figs 6 and 13, the cam follower 64 is a cylindrical element at the outer end of a rod 190 The rod 190 is mounted for axial movement in a 15 radially extending bore 192 at the back end of the bolt 56 The underside of the bolt 56 has a recessed groove 194, and a leaf spring 196 is mounted in the groove 194 so as to engage the lower end of the rod 190 The spring 196 biases the cam follower radially outwardly and into engagement with associated surfaces on the drive cam 60 and, during part of the time that the bolt 56 is in its forward projectile firing 20 position, with associated large diameter surface 206 and smaller diameter surface 208 on the barrel extensions 58 See Fig 24 This will be described in more detail below.

During forward driving movement of the bolt 56, the outer surface of the cam follower 64 is engaged with a surface 199 of the forward driving cam track 160 See 25 Figs 6, 17 and 22 During rearward driving of the bolt 56, the outer surface of the cam follower 64 is engaged with a surface 197 of the spiral cam track 162.

The drive cam 60 has dwell or rest areas at the front and rear ends of the drive cam The dwell areas provide turnarounds at each end of the bidirectional drive cam 30 The rear dwell area includes a surface 201 which is bounded by a rear, radially inwardly extending flange 203 and a forward, inwardly extending flange 205 See Fig 6 This dwell area at the rear of the drive cam holds the bolt 56 in a retracted position from the time that the cam follower 64 leaves the return cam track 162 until the drive cam is rotated to a position in which an opening in the forward flange 205 35 permits the bolt return spring 126 and part 124 to shove the cam follower 64 into the forward drive cam track 160.

In a particular embodiment of the present invention (having the 4 to 1 ratio of drive cam revolutions to control cam revolutions for each cycle of operation as noted above), the cam follower 64 rests at the rear dwell area of turnaround for 0 6 turn of 40 the drive cam 60 The forward drive spiral 160 moves the cam follower forward for 0.8 turn of the drive cam 60 The cam follower moves rearward for 0 8 turn of the drive cam and rests at a forward dwell area for approximately 1 8 turns of the drive cam 60.

When the bolt 56 reaches the forward end of its travel, it must be rotated 450 45 (as illustrated in Fig 13) to lock the lugs 86 on the bolt in front of the lugs 92 of the barrel 52 (see Fig 18).

The construction of the forward end of the drive cam 60 and related structure of the barrel extension 58 and back face of the control cam 62 are best illustrated in the enlarged fragmentary view of Fig 22 50 As best illustrated in Fig 22, when the cam follower i 64 leaves the forward end of the forward drive cam track 160, the back side of the cam follower 64 is positioned in a forward dwell area 198 so that continued rotation of the drive cam 60 cannot produce any continued forward movement of the bolt 56.

The drive cam '60 does, however, have a slot 200 (see Figs 22 and 23) located 55 at the forward, outlet end of the forward cam track 160 so that the spring 196 (see Fig 6) shoves the rear half of the cam follower 64 outward and into this slot 200 as soon as the forward reciprocation of the bolt has been completed The rotation of the drive cam 60 in the clockwise direction indicated by the arrow in Fig 17 then rotates the cam follower and bolt 450 to the locking position illustrated in Fig 18 60 At the same time that the back half half of the cam follower 64 moves into the slot 200, the front half of the cam follower 64 engages the large diameter surface 206 (see Fig 24) of the barrel extension 58 This surface 206 has a ramp 206 a which decreases in diameter, as the bolt is rotated 450 to' the locked position, until the diameter is the same as that 'of the surface 208 This ramp 206 a pushes the cam 65 follower 64 downward from the outwardly extended position shown in phantom outline in Fig 24 to the retracted position shown in solid outline in Fig 24.

The surface 208 thereafter engages the top of the front half of the cam follower 64 to retain the cam follower 64 in the retracted position and within the forward dwell area 198 of the drive cam 60 until the firing of the projectile from the combustion 5 chamber 54 has been completed and the bolt 56 is ready to be rotated back 450 to an unlocked position and then retracted to the projectile loading position by engagement of the cam follower 64 within the rear drive cam track 162.

While the cam follower 64 is retained in the retracted position illustrated in Fig.

24 by the stationary engagement of the cam follower 64 with the surface 208 at the 10 end of the ramp 206, the drive cam 60 is of course continuing to rotate with respect to the cam follower 64 with the back half of the cam follower 64 engaged in the forward dwell area 198 At the same time the rear face 210 of the control cam 62 is rotating counter clockwise with respect to the cam follower 64, as illustrated by the arrows in Figs 18 and 19 15 The rear face 210 of the control cam has a bolt unlocking and return wedge 212 projecting outwardly from the rear face 210 As this wedge rotates into engagement with the cam follower 64, it first of all rotates the cam follower and bolt 450 counter clockwise (as viewed in Fig 20) to unlock the bolt by aligning the lugs 86 with the slots 90 Continued rotation of the control cam 62 then moves the cam follower 64 20 axially to the rear and into the front inlet end of the rear drive cam track 162, as this end of the cam track 162 opens to the forward dwell area 198 Continued rotation of the drive cam 60 then reciprocates the bolt 56 to a rearward, projectile loading bolt position.

The gun 50 as illustrated in the drawings uses a liquid monopropellant, i e a 25 liquid propellant having both a fuel and an oxidizer Mixtures of hydrazine, hydrazine nitrate and water are examples of monopropellants that may be used However, propellants developed for torpedo application have physical, performance, handling and safety characteristics that are well suited for use in the present invention This is understood since torpedo propellants must be compatible with the long duration, closed 30 environment of a submarine where adverse characteristics from the standpoint of toxicity, handling or safety are completely intolerable The liquid propellant is stored, either adjacent to the gun 50 or remotely, and is conducted to the propellant injection means 72 by a flex conduit 216 as shown in Figs 18 and 19 The propellant supply pressure is supplied either by pump or by an accumulator subsystem (not illustrated) 35 The accumulator is preferable from the standpoint of being effective in reducing pump volume requirements while meeting the peak flow rates necessary for burst fire The propellant supply system includes a pressure sensing interlock system (see Fig 44) which senses the propellant pressure by means of a sensor and stops operation of the complete group (row or duster) of gun modules by closing a main propellant supply 40 valve and stopping operation of the drive motor when the supply pressure drops below an established level This prevents incomplete propellant filling.

The porting and valving arrangement for controlling the injection of liquid propellant into the combustion chamber 54 is best shown in Figs 5, 8, 18 and 26-28 of the drawings 45 As best illustrated in Fig 26, the sidewall of the barrel 52 has an axially extending bore 218 at one side of the combustion chamber 54, and the propellant conduit 216 is connected with a port 220 at one end of the bore A port 222 connects the other end of the bore to drain.

A spool valve 224 is mounted for axial movement within the bore 218, and the 50 control of the position of the spool valve 224 is provided by a valve control rod 226 which is connected to the valve spool 224 at one end The other end of the rod 226 is engaged with the front face 96 (see Fig 29) of the control cam 62 and acts as a cam follower.

A port 228 connects the axial bore 218 with the combustion chamber 54 5 The valve spool 224 has annular seals 230 at each end of the spool and the rod 226 is sealed by a seal 232 as illustrated in Fig 26.

The cam face 96 of the control cam 62 is formed with a recessed ramp 234 which controls the duration of the time period for injection of the liquid propellant through the ports 220 and 228 The control rod 226 is biased (by the propellant supply 60 pressure) to the right (as viewed in Fig 26) so that the cam follower end of the rod 226 is maintained in engagement with the face 96 of the rotating control cam 62.

In the firing position, the valve spool 224 is positioned by the control rod 226 to block off the port 228 (as illustrated in Fig 26).

Fig 27 illustrates the position of the valve spool 226 with respect to the port 65 1,582,535 R 228 when the recess 234 of the control cam 62 has been rotated to a position in which the control rod 226 first drops down into the recess 234 The valve spool 224 is shifted to the right in the bore 226 to, open the port 228 for communication with the port 220, and the liquid propellant flows into the combustion chamber under the pressure of the propellant supply system The pressure of the inflowing propellant pumps the 5 projectile 84 forward to the position illustrated in Fig 6 a The inclined ramp in the recess 234 pushes the control rod 226 leftward and back to the position illustrated in Fig 26 as the cam follower end of the control rod 226 returns to the plane of the front face 96 of the control cam 62 The amount of liquid propellant injected is there.

fore determined by the pressure of the propellant supply system and the length and 10 angular inclination of the recess 234.

As illustrated in Fig 29, the front face 96 of the control cam 62 has a projection 94 which is engaged by a spring biased igniter cam follower The electrode 91 is energized as the igniter cam follower is actuated by the projection 94 following the filling of the combustion chamber 54 with the liquid propellant 15 A very important feature of the present invention is the internal water cooling provided by the coolant injection means 73.

The coolant injection means 73 inject a small quantity of water directly into the firing chamber 54 between rounds Since water impinges directly on the heated gun bore surfaces, high heat transfer rates are realized The effectiveness of the internal 20 water cooling permits a significant increase in burst length and frequency in the case of an automatic gun fired at high cyclic rates and permits a significant increase in the length of the duty cycle of guns used at lower cyclic rates such as in common excavation.

In a specific embodiment of the present invention water is used as the cooling 25 liquid because it has a high heat of vaporization and is readily available Other liquid coolants can of course be used, but the description to, follow will be directed specifically toward the use of water as the coolant liquid.

One embodiment of the valve structure for accomplishing the internal water cooling is illustrated in Figs 5 and 26-28 As illustrated in these drawings, the wall 30 of the gun barrel 52 has an axially extending bore 236 A valve spool 238 is mounted for reciprocation within the bore, and the valve spool has seals 240 at each end.

A water inlet port 242 is connected to one end of the bore 236 and a hose is attached to this port 242 to connect the port to a pressurized water supply system.

A port 244 connects the bore 236 to the combustion chamber 54 35 The valve spool 238 is connected directly to, the valve spool 224 through an extension of the rod 226 so that the water coolant valve spool 238 moves in unison with the propellant injection valve spool 224.

Seals 246 and 248 seal off the part of the rod 226 extending between the bores 236 and 218 40 In the firing position of the valve spools (as illustrated in Fig 26) the valve spool 238 blocks flow of water into the port 244 and flow of combustion gases out of the port 244.

Similarly, the water injection valve spool 238 is positioned in the propellant loading position illustrated in Fig27 to block flow through the port 244 45 However, immediately after firing, the control cam 62 rotates to, a position in which a projection 250 shifts the control rod 226 leftward (as viewed in Fig 28) by an amount sufficient to, open the port 244 This projection 250 permits a short time period for the injection of coolant water into the combustion chamber (through the passageway provided by the ports 242, the bore 236 and the port 244) before the S O cam follower end of the control rod 226 moves down off the projection 250 and back onto the plane of the face 96 This small amount of water is vaporized by the hot wall structure of the combustion chamber and turned to steam During this water injection period, the port 228 may be maintained closed by the valve spool 224 or, depending on the size of the projection 250, the port 228 may also be opened for 55 venting of gas and steam from the combustion chamber (through the port 228 and the bore 218 and the vent port 222).

Thus, immediately after firing each round, the coolant injection means 73 are opened and a metered quantity of water is injected directly on the forward portion of the combustion chamber 54 The water spray is directed toward the combustion 60 chamber surfaces of the gun The quantity of water is metered to insure that virtually all of it is converted to steam.

The next projectile 84, in the process of being loaded and pumped forward in the chamber, pushes any steam and water remaining in the chamber ahead of the 1,582,535 projectile into the barrel After firing, the residuals are forced out of the barrel by the projectile as it traverses the bore.

If the distribution of the water vapour in the bore is assumed to be the same as the normal products of combustion of a liquid propellant, the weight of gas (vapour) being pushed out by the projectile is slightly less than that for a conventional solid 5 propellant round This results from the somewhat lower molecular weight of liquid propellant combustion products and that of the water vapour.

The internal water cooling is optimized to inject no more water than is vaporized.

Hence, there is no penalty for acceleration inert mass The water injected is controlled by the dwell of the surface of the projection 250 of the control cam 62 10 Heating and cooling of a gun barrel bore surface is highly transient The analysis of the instantaneous heat transfer process is complex and methods for accurately determing the heat transfer coefficient controlling the process are not well established.

However, the following example, based on average conditions, does illustrated the effectiveness of the internal water cooling 15 Considering a 35 mm 4,000 ft/sec muzzle velocity liquid propellant gun, the significant characteristics are:

Projectile Weight 1 2 lb.

Muzzle Velocity 4,000 ft/sec.

Propellant Charge 1 lb 20 Projectile Muzzle Kinetic Energy 298,000 ft -lb.

Firing Rate 750 rounds per minute Estimates of barrel heating per round are calculated using the criteria established by Corner' where the heat loss Q is:

Q = X ( 1/2 WV') 25 W, = "Effective" Mass of the projectile V = Muzzle velocity X 3 (maximum value) For the characteristics of the 35 mm 4,000 ft/sec LPG, Q = 125,000 ft -lb (or 30 161 B t u).

Gun barrel cooling is accomplished by direct water injection on the interior heated surfaces Assuming initial water temperature to be 701 F, the heat absorption capability of the injected water (including specific heat and heat of vaporization) is approximately 1,110 B t u /lb The quantity of water required for complete cooling after 35 each round is then = 161 B t u /round lb HIO or 146 1110 B t u /lb H 20 round In a rapid fire automatic weapon, the time available for cooling between rounds is limited by heat transfer rate At a firing rate of 750 rounds per minute, the cycle time per round is 80 milliseconds.

The heat transfer rate can be estimated from the following: 40 q = h AAT q = rate of heat transfer B t u /hr.

h = heat transfer coefficient B t u /hr of ft 2 A = area fte AT = temperature difference IF 45 For estimating the heat transfer rate, the following assumptions are made:

a) AT Bore surface temperature rises of 1,200-1,4001 F in one millisecond have been measured in liquid propellant guns at the origin of rifling Since rapid injection of "'Theory of the Interior Ballistics of Guns" J Corner Pg 141 John Wiley & son.

1,582,535 10cooling water immediately after firing is involved in the present method, large average temperature differences will exist during the cooling process Here a conservative AT of 500 OF is assumed.

b) Area The chamber bore' surface area is 375 ff It is assumed that the injected cooling 5 twater is effectively sprayed over an area at least equivalent to this, therefore, the effective area is assumed to be 375 ft 2.

c) Heat Transfer Coefficient Water sprayed against hot surfaces boils violently and is rapidly vaporized Boiling heat transfer coefficients are quite high Coefficients of -300,000 B t u /ft 20 F are 10 common Here, the heat transfer coefficient conservatively is assumed to be 250,000 B t u /hr ft 20 F Based on these considerations, the rate of heat transfer is estimated to be:

q = ( 250,000 B t u) ( 365 fe 2) ( 5000 F) = 4 7 10 ' B t u.

hr fte O F hr.

or 1 3 X 104 B t u 15 sec.

Since complete cooling per round requires removal of 161 B t u the required cooling time is:

161 B t u.

t = 12 4 milliseconds 1.3 104 B t u.

sec.

With a total cycle time per round of 80 milliseconds there is ample cooling time available 20 The above example is idealized in that perfect distribution of the cooling water over the heated surfaces is assumed While complete cooling is not usually attained in practice, a substantial portion of the heat imparted to the gun is removed This has a major impact on firing schedule and gun system effectiveness.

Fig 28 illustrates the disposition of the valve spools 238 and 224 in the event 25 of a misfire, when it is desired to purge' the combustion chamber 54 of all liquid propellant within the combustion chamber In this event, the entire control cam 62 is shifted axially forward by the misfire detection switch 80, and this shoves the control rod 226 leftward to the position illustrated in Fig 28 where the valve spools 238 and 224 are held in the positions illustrated The coolant water flows continuously 30 into the combustion chamber through the coolant inlet port 244, fills the combustion chamber 54 completely with water, and purges out all of the liquid propellant through the port 228 and the, vent 222.

A timing device, not illustrated, shuts off the flow of water through the hose 241 (see Fig 7) after a period of time sufficient to insure complete purging of the 35 combustion chamber.

As described above in this specification, the misfire switch 80 is controlled by the misfire detection means 78 (see Fig 5).

The misfire detection means 78 include a gas piston 252 mounted for reciprocation within a cylinder 254 and spring biased by a spring 256 rightward (as viewed in Fig 40 5) to the position illustrated in Fig 5 where a flange 258 engages a snapring stop 260.

A connecting rod 262 connects the gas piston 252 to the misfire switch 80 so that the misfire switch 80 is normally spring biased to the position illustrated in Fig 5 in which the misfire switch 80 is axially aligned with the lobes 184 on the control cam 62 45 A port 264 connects the bore of the barrel 52 with the interior of the cylinder 254 at the back face of the gas piston 252.

A vent port 266 is located in the sidewall of the cylinder to vent the interior of the cylinder 254 to, atmosphere.

As a projectile is fired from the gun, the pressurized gases behind the projectile 50 flow through the port 264 to momentarily move the gas piston 252 forward (leftward as viewed in Fig 5) within the cylinder 254 This pulls the misfire switch 80 forward 1,582,535 and out of alignment with the lobe 184 on the control cam long enough to let this lobe rotate past the misfire switch without engaging the misfire switch 80.

However, if there is a misfire, the gas piston 252 remains stationary and the misfire switch 80 engages the cam lobe 184 to divert the cam lobe into a dead side track 187 (see Fig 43 and Fig 6) while the other cam lobe 184 enters a relieved area 5 This moves the control cam 62 axially forward in the recess 188 (see Fig 6) to disengage the gear 178 from the idler gear 176, and the rotation of the control cam 62 is stopped.

The timing of this action leaves the bolt 56 in a locked position with the breach closed 10 In addition, as pointed out above, forward motion of the control cam 62 pushes the propellant fill valve spool 224 forward, exposing the combustion chamber fill port 228 to the port 222 at the rear of the bore 218 to permit purging of the liquid propellant from the combustion chamber 54 At the same time the water inlet valve spool 238 is moved forward to open the water injection port 244, and water is purged 15 through the combustion chamber 54 to prevent cook off and to make the round inert.

The control cam disengagement disables that particular gun module but it does not disable the drive cam power train Therefore, other modules in the banked row or cluster continue to operate and fire Operation in this limited condition can con 20 tinue until servicing Projectiles intended for loading but passing over the disabled module are ejected at the end of the feed system transfer region.

If a projectile is missing at the feed system conveyor, a mechanical interlock system leaves a retainer in the path of the propellant fill valve spool 224 to prevent the valve from opening As the module continues in a cycle of operation, a pseudo 25 misfire occurs, and the module is disabled as described above.

Since complete propellant filling depends on fluid pressure in the propellant supply system with the monopropellant injection system described above, insufficient pressure of the propellant supply system could result in incomplete propellant filling In the present embodiment when the supply pressure inadvertently drops below an established 30 level, a pressure sensing interlock system (see Fig 44) stops operation of the complete group (row or cluster of modules).

The projectile feed system is best shown in Fig 31.

The projectile feed mechanism 68 employs a short endless conveyor 149 which is driven by a sprocket drive 270 from the drive motor 164 35 As best illustrated in Fig 32, the conveyor 140 mates with a transfer mechanism 272 to accept projectiles 84 from a conventional belt or linkless feed The transfer mechanism 272 includes a shifting device which selects from separate projectile supplies to switch types of ammunition The spring clip cradles 146 are the primary elements of the conveyor 149 The tangs on the ends of the spring clip cradles slide 40 in guide grooves in the conveyor frame The cradles are coupled to form an endless, flexible chain.

Two configurations of the conveyor 149 are illustrated in Figs 31-32 and in Fig 33 In Figs 31 and 32 a flat conveyor passing over a banked row of modules is illustrated and in Fig 33 a circular conveyor wrapping around a cluster of three 45 modules is illustrated.

The flat conveyor configuration shown in Figs 31 and 32 demonstrates the loading scheme of the present invention which depends on a unique sequencing arrangement In Fig 32 is illustrated a banked row of five modules, each served by the conveyor 149 and indicated by the reference numerals 1-5 The projectiles 84 move 50 along the conveyor from right to left and are numbered in groups of five, e g ( 5, 4, 3, 2, 1), ( 10, 9, 8, 7, 6), etc The modules are also numbered ( 5, 4, 3, 2, 1) and are loaded in the sequence 1 to 5 and fire, of course, in the same sequence Centreto-centre spacing of the projectiles in the conveyor ( 1 75 in for 30 mm) is 1/2 the centre-to-centre spacing of the modules ( 3 5 infor 30 mm) 55 Assume projectile 1 is at the loading position for module 1 The loading lever on the module kicks the projectile out of the conveyor and into the module The conveyor travels 1 75 inches between loadings Projectile 2 was 1 75 inches away from the loading position for module 2 at the start but has now arrived in position and is loaded Projectile 3 is now 1 75 inches away from the module 3 and will arrive at the 60 loading position on time The loading progresses until projectile 5 is loaded in module 5, this projectile having moved 7 0 inches while the other projectiles were loading.

By the time projectile 5 has been loaded, projectiles 10, 9, 8, 7 and 6 have moved into positions occupied by projectiles 5, 4, 3, 2 and 1 at the start The process continues in perfect time, with projectile 6 loading into module 1, projectile 7 loading 65 1,582,535 into module 2, etc T 1 his loading scheme applies to any number of modules.

The circular conveyor for a cluster of three modules, shown in Fig 33, uses the same loading scheme as described above Since the conveyor is circular, the cradles can take the form of pockets in a wheel-like structure A minimum of six cradles or pockets are needed to, properly feed the cluster Nine pockets are shown in Fig 33 5 to reduce the rotational speed of the conveyor and the centrifugal force imposed on the projectiles, thus reducing the force that must be exerted by the projectile loading levers at the modules.

Other cluster configurations as illustrated in Figs 34-39 are readily arranged and serviced by the projectile loading mechanism 68 as described above 10 The modular system as described above can accommodate recoil adapters similar to those on the M-61 gun to reduce recoil forces A banked row or duster of modules can, be supported mutually at the breach end of the barrels by a bracket structure that receives a pair (or more) of recoil adapters An additional bracket structure mutually supports the rear of the modules and engages a short fixed slide to accommodate recoil 15 travel The latter bracket includes a provision for boresighting.

The impact of caseless operation on gun design is best illustrated in Fig 41 which compares a 30 mm liquid propellant modular gun projectile with a conventional 20 mm round for the M-61 gun Due to the similarity in length and diameter between the liquid propellant projectile and the solid propellant round, it is feasible to substitute 20 directly the 30 mm projectile for the existing 20 mm cartridge Some modifications are, of course, required due to slight differences in configuration but the overall volume is substantially the same. Fig 40 compares the diameters of a liquid propellant modular gun

projectile in a 30 mm size with the cartridge and projectile size for a conventional 30 mm solid 25 propellant round This figure illustrates the space savings which can be achieved for the projectile feed systems in the 30 mm gun size with the liquid propellant modular gun of the present invention.

While we have illustrated and described the preferred embodiments of our invention, it is to be understood that these are capable of variation and modification, and 30 we therefore do not wish to be limited to the precise details set forth, but desire to avail ourselves of such changes and alterations as fall within the purview of the following claims.

Claims (1)

1. WHAT WE CLAIM IS:-

   1 A gun of the kind in which liquid propellant is burned in a combustion chamber 35 to fire a projectile from the gun and comprising a gun barrel, a combustion chamber, a bolt mounted for axial movement between a rearward, projectile loading position and a forward, projectile firing position, liquid propellant injection means for injecting a liquid propellant into the combustion chamber, igniter means for igniting the liquid propellant in the combustion chamber, drive cam means for moving the bolt back and 40 forth between the rearward and forward positions, drive means for driving the drive cam means, and control means for controlling the liquid propellant injection means and igniter means in coordination with the drive of the drive cam means.

   2 A gun according to' Claim 1 wherein the drive cam means include a rotatable drive cam member and the control means include a rotatable control cam member 45 3 A gun according to Claim 2 wherein the drive means include gears interconnecting the drive cam member and control cam member for rotation in synchronism.

   4 A gun according, to any one of the preceding claims including a receiver, guide slots in the receiver, bolt lugs engageable in the guide slots, locking lugs in the barrel and bolt locking means for rotating the bolt lugs into engagement with the locking 50 lugs in the barrel to, carry the combustion chamber firing loads through the barrel rather than through the receiver.

   A gun according to' any one of the preceding claims wherein the drive cam means include a bolt locking surface for rotating the bolt tol a locked position at the forward, projectile firing position 6 A gun according to any one of the preceding claims wherein the control cam means include a bolt unlocking surface for rotating the bolt to an unlocked position after the firing of a projectile and prior to the movement of the bolt to the rearward, projectile loading position.

   7 A gun according to any one of the preceding claims wherein the drive cam 60 member and the control cam member are rotatable about axes which are parallel to the axes of reciprocation of the bolt, the bolt includes a cam follower, and the drive cam means include a first spiral cam track engageable with the cam follower to' drive 1,582,535 the bolt forward and a second spiral cam track engageable with the cam follower to drive the bolt rearwardly.

   8 A gun according to Claim 7 wherein the drive cam means include dwell areas at the front and rear of the drive cam means for permitting rotation of the drive cam means without producing axial movement of the bolt 5 9 A gun according to Claim 8 wherein the drive cam means include a hollow cylindrical drive cam member having a longitudinal axis concentric with the axis of reciprocation of the bolt and wherein the bolt is mounted for axial movement within the interior of the drive cam member.

   10 A gun according to any one of Claims 7 to 9 including biasing means associated 10 with the bolt for biasing the bolt and cam follower forward to cause the cam follower to enter an open end of the first spiral cam track.

   11 A gun according to Claim 10 wherein the biasing means include a spring engageable with the rear end of the bolt.

   12 A gun according to Claim 11 including sear means for holding the bolt in 15 the rearward position against the force of said spring until the sear is released.

   13 A gun according to any one of Claims 9 to 12 wherein the cam follower is mounted for sliding movement radially inward and outward of the bolt and including biasing means normally biasing the cam follower radially outwardly of the bolt, a slot in the front dwell having a sidewall engageable with the cam follower for rotating 20 the bolt to a locked position, and receiver cam means for depressing the cam follower radially inwardly of the bolt and out of engagement with said sidewall after the bolt is rotated to the locked position.

   14 A gun according to Claim 13 wherein the control means include a hollow annular member having a forward cam face and a rearward cam face, and including 25 an axially projecting surface on a part of the rear cam face for engaging the cam follower to rotate the bolt to an unlocked position and to move the cam follower into the second spiral cam track.

   A gun according to Claim 14 wherein the drive means are connected to rotate the drive cam member faster than the control cam member and in a direction opposite 30 to the rotation of the control cam member.

   16 A gun according to any one of the preceding claims wherein both the control cam member and the drive cam member are annular, cylindrical members, the control cam member is positioned at the forward end of the drive cam member, the bolt is mounted for reciprocation back and forth within the interior of the drive cam and 35 control cam members, the bolt includes a radially extending cam follower, the drive cam member includes a first internal spiral cam track engageable with the cam follower to drive the bolt forward and a second internal spiral cam track engageable with the cam follower to drive the bolt rearward, the drive cam member includes dwell areas at the front and rear for permitting rotation of the drive cam member without pro 40 ducing axial movement of the bolt and wherein the control cam member has a rear face formed with an axially projecting bolt return surface engageable with the cam follower to move the cam follower into the second spiral cam track.

   17 A gun according to any one of the preceding claims wherein both the drive cam member and the control cam member have gears formed on their outer periphery 45 and the drive means include a first gear engageable with the drive cam gear, a second gear engageable with the control cam gear, and an interconnecting drive shaft connected to drive both the first gear and the second gear.

   18 A gun according to Claim 17 wherein the control cam member is axially movable into and out of drive engagement with the second gear and including misfire 50 detection means for moving the control cam member out of driving engagement with the second gear in the event of a misfire.

   19 A gun according to claim 18 wherein the misfire detection means include a port through the sidewall of the barrel, a spring biased gas piston mounted for movement against the spring bias by the pressure of combustion gases passing through the 5 5 port in the barrel, a misfire switch engageable with the control cam member to, disengage the control cam member from drive by the second gear, and a connecting rod extending between the gas piston and the misfire switch for retracting the misfire switch to a position in which the misfire switch cannot engage the control cam member when the gas piston is moved against the spring bias 60 A gun according to claim 19 including a lug on the control cam member for engagement with the misfire switch.

   21 A gun according to any one of the preceding claims including liquid coolant injection means for injecting a liquid coolant into the combustion chamber to cool the combustion chamber structure after the firing of each round 65 1,582,535 ' 22.Agunccoringocaim 1 wh 2 re 35 h u l 22 A gun according to claim 21 wherein the liquid coolant is water.

   23 A gun according to claim 21 or claim 22 wherein the liquid coolant injection means include valve means operatively associated with the control means for controlling the timing and amount of liquid coolant injected.

   24 A gun according to any one of claims 21 to 23 wherein said liquid coolant 5 injection means includes a coolant inlet port, a coolant control valve associated with the coolant inlet port and a control rod having one end connected to the coolant control valve and the other end engaged with the control means.

   A gun according to, claim 24 wherein the coolant control valve is a spool type valve and is mounted for sliding movements within a cylindrical bore 10 26 A gun according to claim 25 including a purge outlet port connected to the cylindrical bore in which the propellant control valve is slidable for permitting the flow of purge liquid out of the propellant injection means and purge outlet port after a misfire of the gun.

   27 A gun according to any one of claims 24 to 26 wherein the control means 15 include an annular cam member having a front surface engaged with the control rod and including a projection on said front surface for momentarily opening the coolant inlet valve.

   28 A gun according to any one of claims 23 to 27 including misfire detection means for pulling the entire control cam member and coolant inlet valve forward to 20 a position in which the coolant control valve remains open to, permit a purging of propellant from the combustion chamber in the event of a misfire.

   29 A gun according to any one of claims 21 to 28 wherein the liquid propellant injection means and the liquid coolant injection means are connected together for movement in unison by a common control rod 25 A gun according to claim 29 wherein the propellant injection means, the coolant injection means and the control rod cooperate in a manner such that the coolant does not flow into, the combustion chamber when the propellant flows into the combustion chamber, and the propellant does not flow into the combustion chamber when the coolant flows into the combustion chamber 30 31 A gun according to claim 30 wherein the liquid propellant injection means and liquid coolant injection means are operatively associated with the control means for positioning the propellant injection means and coolant injection means in a first position in which the flow of both liquid propellant and liquid coolant into and ont of the combustion chamber is blocked during firing of the gun, in a second position 35 in which the flow of liquid propellant is permitted into the combustion chamber and the flow of liquid coolant into the combustion chamber is blocked during propellant injection prior to firing, and a third position in which the flow of liquid propellant into the combustion chamber is blocked while the flow of liquid coolant into the combustion chamber is permitted for cooling and purging of the combustion 40 chamber.

   32 A gun according to any one of the preceding claims wherein the liquid propellant injection means inject a monopropellant into the combustion chamber.

   33 A gun according to claim 32 wherein the control means include an annular control cam member mounted for rotation about an axis concentric with the axis of 45 reciprocation of the bolt and having a forward generally planar extending surface formed with a recessed ramp, the propellant injection means include a propellant fill port, a control valve for the fill port, a rod having one end connected to the fill valve and another end engaged with said forward face of the control cam member, and pressure means for supplying the liquid monopropellant through the propellant fill so port during the time that the control rod is engaged with the recessed ramp on the control cam means.

   34 A gun according to claim 33 wherein the propellant control valve is a spool type valve and is mounted for sliding movements within a cylindrical bore.

   35 A gun according to any one of the preceding claims including a receiver, a 55 projectile loading passageway in the receiver, a projectile feed system including a spring clip for each projectile, and projectile loading means including a projectile loading lever movable to snap a projectile out of its spring clip and into the projectile loading track in the receiver in response to reciprocation of the bolt to its rearward projectile loading position 60 36 A gun according to' claim 35 wherein the projectile loading lever includes a bellcrank member and the projectile loading means include an actuator lever engageable with the bolt and a push rod operatively connected to the bellcrank member at one end and to the actuator lever at the opposite end.

   37 A gun according to' claim 35 or 36 wherein the projectile feed system includes 65 1.581535 1 s an endless conveyor made up of said spring clips.

   38 A gun according to any one of the preceding claims comprising cyclic means for automatically loading the individual projectiles one-by-one in sequence so long as the gun is operated in a trigger on condition.

   39 A gun according to any one of the preceding claims wherein the gun is a gun 5 module and includes receiver means having an external configuration which permits the gun module to be mounted with other gun modules in patterned groupings to form a modular gun comprising a plurality of individual gun modules and with the receiver means of adjacent gun modules engaged in mutual support.

   40 A gun according to claim 38 wherein the drive means include an idler gear 10 for transferring drive from one gun module to an adjacent gun module so that all of the gun modules in a cluster can be driven from a single drive motor.

   41 A modular gun comprising a plurality of gun modules, each of the gun modules comprising a gun according to any one of the preceding claims and wherein the receiver means of each gun module have an outer shape which permits a plurality 15 of gun modules to be arranged in patterned groupings with the receiver means of adjacent modules engaged in mutual support.

   42 A method of firing a projectile from a gun of the kind in which a liquid propellant is burned in a combustion chamber, said method comprising the steps of locating a projectile in said gun, moving a bolt axially from a rearward, projectile 20 loading position to a forward, projectile firing position by a drive cam means driven by a drive means, injecting liquid propellant into the combustion chamber, igniting the liquid propellant in the combustion chamber, the injection and ignition of the liquid propellant being controlled in coordination with the drive means, and thus in coordination with movement of the bolt 25 43 A method of firing a projectile according to claim 42 further comprising the step of injecting a liquid coolant into the combustion chamber after the firing of the projectile, the coolant being directed against the sides of the combustion chamber to vaporise the coolant.

   44 A method of firing a projectile according to claim 43 further comprising the 30 steps of blocking, by means of a propellant control valve, the flow of propellant into the combustion chamber during the coolant injection, and permitting the flow of fluids out of the combustion chamber through a purge outlet opening, said opening being normally closed by the propellant control valve.

   45 A method according to claim 44 including detecting whether a misfire has 35 occurred and, subsequent to the detection of a misfire, opening said purge outlet for long enough to permit the combustion chamber to be filled with liquid to purge propellant out of the combustion chamber.

   46 A method of firing projectiles according to claim 42 or 43 from a gun of the kind having a cyclic mechanism for automatically loading and firing individual pro 40 jectiles one-by-one in sequence so long as the gun is operated in a trigger on condition, said method comprising detecting whether a misfire of a projectile has occurred during the automatic firing mode of operation, and stopping operation of the cyclic mechanism, after detection of the misfire, by moving a mechanical part of the cyclic mechanism out of operative engagement with the rest of the cyclic mechanism 45 47 A gun substantially as herein described with reference to and as shown in Figures 1, 4-30 and 42-44 of the accompanying drawings.

   48 A gun substantially as herein described with reference to and as shown in Figure 2 of the accompanying drawings.

   49 A gun substantially as herein described with reference to and as shown in 50 Figure 3 of the accompanying drawings.

   A gun substantially as herein described with reference to and as shown in Figures 31 and 32 of the accompanying drawings.

   51 A gun substantially as herein described with reference to and as shown in Figure 33 of the accompanying drawings 55 52 A gun substantially as herein described with reference to and as shown in Figure 34 of the accompanying drawings.

   53 A gun substantially as herein described with reference to and as shown in Figure 35 of the accompanying drawings.

   54 A gun substantially as herein described with reference to and as shown in 60 Figure 36 of the accompanying drawings.

   A gun substantially as herein described with reference to and as shown in Figure 37 of the accompanying drawings.

   56 A gun substantially as herein described with reference to and as shown in Figure 38 of the accompanying drawings 65 1,582,535 1,582,535 57 A gun substantially as herein described with reference to and as shown in Figure 39 of the accompanying drawings.

   58 A method of firing a projectile substantially as herein described with reference to the accompanying drawings.

   FORRESTER, KETLEY & CO, Chartered Patent Agents, Forrester House, 52 Bounds Green Road, London, Nil 2 EY -and also atRutland House, 148 Edmund Street, Birmingham B 3 2 LD, Scottish Provident Building, 29 St Vincent Place, Glasgow G 1 2 DT, Agents for the Applicants.

   Printed for Her Majesty's Stationery Office by the Courier Press, Leamington Spa, 1981.

   Published by the Patent Office, 25 Southampton Buildings, London, WC 2 A l AY, from which copies may be obtained.